The disclosure relates generally to apparatus for reducing turbulence in a fluid stream and damping pressure pulsations propagated by the fluid. More particularly, the disclosure relates to a flow straightening device that reduces turbulence in moving fluid. Still more particularly, it relates to a flow straightener that reduces turbulence of drilling fluid passing through a mud pump and that dampens pressure pulsations propagated by the drilling fluid.
To form an oil or gas well, a bottom hole assembly (BHA), including a drill bit, is coupled to a length of drill pipe to form a drill string. Instrumentation for performing various downhole measurements and communication devices are commonly mounted within the drill string. The drill string is then inserted downhole, where drilling commences. During drilling, fluid, or “drilling mud,” is circulated down through the drill string to lubricate and cool the drill bit as well as to provide a vehicle for removal of drill cuttings from the borehole.
Mud pumps are commonly used to deliver drilling mud to the drill string during drilling operations. Many conventional mud pumps include a piston-cylinder assembly hydraulically coupled to a compression chamber disposed between a suction module and a discharge module. The suction module is coupled to a suction manifold through which drilling mud is supplied to the mud pump, and the discharge module is coupled to a discharge manifold into which pressurized drilling mud is exhausted from the mud pump. The suction module includes a valve which is operable to allow or prevent the flow of drilling mud from the suction manifold into the compression chamber. Similarly, the discharge module includes a valve which is operable to allow or prevent the flow of pressurized drilling mud from the compression chamber into the discharge manifold. Each valve has a closure member or poppet that is urged into sealing engagement with a sealing member or seat by a biasing member, such as a spring.
During operation of the mud pump, the piston reciprocates within its associated cylinder. As the piston moves to expand the volume within the cylinder, the discharge valve closes, and suction valve opens. Drilling mud is drawn from the suction manifold through the suction valve into the compression chamber. When the piston reverses direction, decreasing the volume within the cylinder and increasing the pressure of drilling mud contained with the compression chamber, the suction valve closes, and the discharge valve opens to allow pressurized drilling mud from the compression chamber into the discharge manifold. While the mud pump is operational, this cycle repeats, often at a high cyclic rate, and pressurized drilling mud is continuously fed to the drill string.
Due to the reciprocating motion of the mud pump piston, cyclic loads are transferred to the suction module by virtue of its coupling to the mud pump, The transferred loads cause cyclic deformation of the suction module. Consequently, pressure pulsations are created within and propagated by the drilling mud passing therethrough.
Additionally, because the suction module typically includes piping elbows, bends, and “Ts,” drilling mud flowing from the suction manifold into the suction module, upstream of the suction valve, is often highly turbulent. When the suction valve opens, the turbulent drilling mud flows rapidly into the compression chamber. Due to the turbulent nature of the drilling fluid, bubbles form within the compression chamber as the drilling fluid flows rapidly around the suction valve poppet. When the piston subsequently compresses the drilling mud within the compression chamber, these bubbles burst, creating additional pressure pulsations within the drilling mud.
The formation of bubbles within the compression chamber due to the turbulent nature of drilling mud passing around the suction valve poppet reduces the efficiency of the mud pump. Moreover, pressure pulsations created within and carried by the drilling mud disturb downhole communication devices and instrumentation, and potentially degrade the accuracy of measurements taken by the instrumentation. Over time, the pressure pulsations may also cause fatigue damage to the drill string pipe.
Accordingly, there is a need for apparatus that reduces turbulence within drilling mud systems and that dampens pressure pulsations caused by the reciprocating motion of mud pumps coupled thereto.